Transport means for sheets

ABSTRACT

A transport roller for forwarding sheets bearing unfused electrostatographic images in copying apparatus comprises a core with a coiled spring wound therearound, the axis of the coils surrounding the core. When the roller is used a minimal distortion or smearing of the powder images occurs.

United States Patent 1191 Mihalik 4 [4 1 Feb. 12, 1974 TRANSPORT MEANSFOR SHEETS [56] References Cited [75] Inventor: Nandor Mihalik, UNITEDSTATES PATENTS u -T England 623,285 4/1899 Marshall 29/126 [73]Assignee: Gestetner Copiers Limited, 5:323 198/192 A Tottenham, London,England [22] Filed: Nov. 15, 1972 Primary Examiner-Joseph E. Peters, Jr.

Assistant Examiner-Kenneth C. Hutchison [21] Appl' 306872 Attorney,Agent, or Firm-F1eit, Gipple & Jacobson [30] Foreign ApplicationPriority Data [57] ABSTRACT NOV. 18, 1971 Great Britain A transportroller for forwarding sheets bearing un M fused electrostatographicimages in copying apparatus "355/3 R29/ comprises a core with a coiledspring wound there 11 d, th f th th 58 Field of Search 355/3 R, 3 DD,17; 271/51, arou" e 0 e surmu mg e we When the roller is used a minimaldistortion or smearing of the powder images occurs.

7 Claims, 2 Drawing Figures PATENTED FEB I 2 I974 TRANSPORT MEANS FORSHEETS This invention relates to transport means for sheets. Inparticular the invention relates to a transport roller for forwardingsheets of paper bearing unfused electrostatographic powder images.

In common forms of electrostatographic copying apparatus, anelectrostatic image is formed on a photoconductive surface, such as thesurface of a drum, by charging the drum and exposing it to a lightimage, so

that it is selectively discharged. The image is then developed by one ofthe well known methods such as by cascading toner particles over thesurface of the drum such that they adhere to the charged areas of thedrum in the image pattern. The so developed image is then transferred toa copy sheet, such as a sheet of paper, which is urged against thesurface of the drum. The sheet is subsequently forwarded to a fusingzone, wherein heat fusing or solvent vapour fusing of the powdered imagetakes place. The sheet must be trans ported from the station whereat itcontacts the drum to the fusing zone and this transportation can presentdifficulties caused by the unfused powdered image bea coming smeared orotherwise disturbed. Thus, the

toner material may itself be disturbed, and the electrostatic image mayalso be disturbed, particularly in dry developing situations, where, incontrast to wet development, no insulating liquid is present to protectthe electrostatic image. Such a liquid, in wet developing, protects theelectrostatic image and also protects the toner from a roller surface.

We have found that a sheet bearing an unfused elec- I trostatog raphicpowder image can be forwarded without the image becoming smeared by atransport means including a transport roller which comprises a coreabout which is wound a coil spring with the axis of the coils of thespring surrounding the core.

Thus, the present invention provides a transport roller for forwardingsheets bearing unfused electrostatographic powder images including acore about which is wound a coil spring with the axis of the coilsof thespring surrounding the core.

While the invention can be applied to both wet and dry developed copysheets, and any other type of sheet, it is particularly advantageouswith dry development where difficulty has previously been particularlyencountered in forwarding copy sheets.

Suitably, the axis of the coils of the spring is itself disposed inhelical form about the-core, and the spacing between successive turns ofthe spring around the core may suitably be such that they very nearlytouch or do so.

The spring is preferably electrically conductive and it is preferablymade of wire. The spring is suitably stretched under light tension andsuitably may be fixed at each end by means of the wire of which it isformed being inserted through a hole in the core. One suitable form ofroller comprisesa core of three-eighths inch diameter with a wire coilspring of outside diameter one-eighth inch wound around it. The overalloutside diameter of the roller is then five-eighths inch; suitably thediameter of the vwire is between 0.01 and 0.05 inches, and preferably003 inches. The spring may be stretched so that at the core surface thedistance between the wire in adjacent coils of the spring is equal tothe wire diameter.

The invention also provides an electrostatographic copying machinewherein electrostatic images are formed and developed with tonerparticles and are then transferred to copy sheets, including such aroller for forwarding the copy sheets.

The roller may be provided in a forwarding arrange ment to co-operatewith any other sort of roller or surface provided that the imaged sidesof the sheets contact the roller with the coil spring. It is howeverpossible to provide two such rollers to co-operate for forwardingsheets, and this will particularly be useful in cases where doubleimages are provided, one on each side of the sheet. The diameter of therollers may be selected according to the size of machine and speed offorwarding required. I

The reason why rollers of the invention are satisfactory for forwardingsheets bearing unfused images is not entirely clear at present. It maybe that it is the fact that there is an incomplete outer surface in theouter envelope of the roller which is important, as the sheet andunfused image will only be contacted over a part of their areas whenforwarded by the roller. This part or point contact may also be expectedto be associated with an apparent lack of disturbance of theelectrostatic field which holds the toner on the sheet during forwardingin contrast to a roller with a complete surface which might itselfbecome charged, and thus create such a disturbance. A lack ofdisturbance of the image would, we believe follow from this feature. Itmay again be that it is the resilience of the rollers which isimportant, or, again that the various factors are to gether required ina satisfactory roller. While individual coils of the spring may deformradially they will probably be tangentially movable more easily.Accordingly, it may, again, be the case that, when forwarding a sheet,the coils adjust their position slightly to avoid contact with imagematerial on the sheet.

In order that the invention may be more clearly understood, thefollowing description is given by way of example only with reference tothe accompanying drawings in which:

" FIG. 1 is a longitudinal side view of one form of roller according tothe invention; and

FIG. 2 is a sectional view taken upon the line AA of FIG. 1;

The roller shown in FIGS. 1 and 2 of the drawings comprises a core 1surrounded by a wire coilspring 2. Hub shafts 4 extend from the end ofthe core 1. The hub shafts extend into bearings in frame members 7 of anelectrostatographic copying machine. For clarity the frame members areshown cut away and other parts of the machine, which are familiar tothose skilled in the art are again not shown for clarity. The spring 2is fixed on the core by the wire of the spring having a straight portion3 inserted through a hole 5 in the core at each end thereof. An end ofthe straight portion is bent to prevent unwanted withdrawal. The springis wound in helical fashion around the core under light tension, and onthe interior of the winding at the surface of the core adjacent coils ofwire are approximately a distance apart equal to their diameter.Successive windings touch or nearly touch. A roller of the typeillustrated has been fitted into a electrostatographic copying machinebetween the image transfer point and the fusing unit, and was driven inco-operation with a rubber roller and with a slight pressurethereagainst. Over 25,000 copies were made and passed between the tworollers without any effect on the unfused tained on the sheets.

I claim:

1. An electrostatographic copying machine wherein electrostatic imagesare formed and developed with toner particles and are then transferredto a copy sheet, said machine including a transport roller forforwarding sheets bearing unfused powder images, said transport rollerhaving an axis about which it is rotatable and comprising in combinationan elongate core extending lengthwise of said axis and a coil spring,having convolutions wound about an axis said coil spring axis beingwound in turns around said core.

2. A copying machine as claimed in claim 1 and wherein said axis of saidcoil spring is helically disposed around said core.

3. A copying machine as claimed in claim 1 and powder images conwhereinsuccessive turns of said coil spring longitudinally of said core touchone another.

4. A copying machine as claimed in claim 1 and wherein the spacing ofsuccessive turns of said coil spring along said core is such thatsuccessive turns are closely spaced.

5. A copying machine as claimed in claim 1 wherein said spring is ofwire.

6. A copying machine as claimed in claim 1 wherein said spring isstreched under light tension about said core.

7. A copying machine as claimed in claim 6 wherein the coil springcomprises convolutions of a filament touching said core with thedistance between adjacent convolutions of the spring where they touchthe core being equal to the diameter of said filament.

1. An electrostatographic copying machine wherein electrostatic imagesare formed and developed with toner particles and are then transferredto a copy sheet, said machine including a transport roller forforwarding sheets bearing unfused powder images, said transport rollerhaving an axis about which it is rotatable and comprising in combinationan elongate core extending lengthwise of said axis and a coil spring,having convolutions wound about an axis said coil spring axis beingwound in turns around said core.
 2. A copying machine as claimed inclaim 1 and wherein said axis of said coil spring is helically disposedaround said core.
 3. A copying machine as claimed in claim 1 and whereinsuccessive turns of said coil spring longitudinally of said core touchone another.
 4. A copying machine as claimed in claim 1 and wherein thespacing of successive turns of said coil spring along said core is suchthat successive turns are closely spaced.
 5. A copying machine asclaimed in claim 1 wherein said spring is of wire.
 6. A copying machineas claimed in claim 1 wherein said spring is streched under lighttension about said core.
 7. A copying machine as claimed in claim 6wherein the coil spring comprises convolutions of a filament touchingsaid core with the distance between adjacent convolutions of the springwhere they touch the core being equal to the diameter of said filament.